Method of and means for controlling alternating currents



July 5, 1927.

' 1,634,970 E. F. w. ALEXANDERSON I usrnon or AND mums FOR CQNTROLLING ALTERNATING CURRENTS Original Filed Nov. 20, 1914 [Ill 7 Invenbor: Ernst. FW/Mexandersoh;

His Attorney. I

Patented Jilly 5, 1927. v

. UNITED STATES,

: 1,634,970 PATENT OFFI'CE.'

mar r. w. u'nxmnnson, or sonnnnoranv, NEW YORK, nssrenoa ro GENERAL LECTRIC COMPANY, A oonronnrron or NEW Yonx.

HE'II IIO D OF AND MEANS FOR CONTROLLING ALTEBNATING GUBRENTS.

Original application filed November 20, 1914, Serial application filed May 24,

My present invention relates to improve ments in apparatus for controlling alternating electric currents, and more especlally for controlling alternating currents used in wireless signaling systems. My present application is a division of my prior appl1cation Serial No. 873,110, filed November 20, 1914, now Patent No. 1,522,221. The object of my invention 1s to provide a suitable organization whereby the amplitude oflalternating current flowing in a c1r-- cuit or the output of an alternating current generator of comparatively large capac ty may be varied between wide limits by variations in a controlling current of comparatively small magnitude.

A further object of my invention is to provide a transmitting system for wireless telephony wherein large amounts of energy may be controlled by the small current variations produced by sound waves m an ordinary telephone transmitter, in such a way that the sound waves may be faithfully reproduced in suitable receiving apparatus at a distant point. The utility of myunvention, however, is by no means limited to wireless telephony as it may equally well be employed in transmitting telephone currents through wires.

The novel features which I believe to be characteristic of my invention are pointedout with particularity in the appended claims. The invention; itself, however, with further objects and advantages will best be understood by reference to the followmg description taken in connection with the accompanying drawing, in which I have shown a simple diagrammatic representation of the apparatus and. circuit connections which may be employed in carrying my invention into eifect.

As indicated in the drawing, the source I of high frequency alternating current 1 is inductively connected by means of the transformer 2 with the antenna 3. The amount of current flowing in the antenna is controlled by varying the inductance of the antenna circuit by variations in a controlling current flowing in a second circuit. As here indicated, a reactance comprising the two -'-coi1s 4 and 5 Wound around a magnetic core 6 is connected in shunt to t a secondary of transformer 2. Wound upo; the same core are twoicoils 7 and 8 through which the con- No. 873,110, Patent No. 1,522,221. Divided and this 1924. Serial 130,715,723.

trolling current is caused to flow. The coils 7 and 8 are connected in opposition to each other, hence, the magnetizing action of the current flowing in coil 7 upon coil 5 is opposite in effect to that of the current flowing in coil 8 upon coil 4. Furthermore, as coils 'Z and 8 are connected in opposition, the voltage i nduced in coil 7 by the high frequency current is opposite to that induced in coil 8. The respective coils areso designed that the voltage induced in coil 7 is equal to that induced in col] 8 and therefore the effect of these voltages is neutralized. The com bined inductance of coils 4 and 5 will vary as a function of the variations in the magnetization of the core 6, this change in inductance beingdue to the varying magnetic reluctance at varying magnetic densities} Since the coils 7 and 8 are connected in opposition, the combined inductance of coils 4' I and 5 in the shunt circuit will be uniform for the two alternations of a complete cycle of the current. ,It will thus be evident that the current flowing-in the antenna can be controlled by varying the amount of current supplied to the coils 7 and 8.

In the parent application, one modification is shown in which the inductance of coils 4 and 5 is inserted in series in the antenna circuit. This arrangement has certain disadvantages which may be overcome by connecting the coils 4 and 5 in shunt to,

the antenna circuit as indicated. With the circuit connections shown, if the apparatus is so adjusted that the natural period of the antenna is slightly below the frequency of the source 2, an increase in the controlling current will produce a decrease in the inductance of the coils 4 and 5. This will produce an increase in the current flowing through these coils with a consequent drop in the potential applied to the antenna. As

a result the amplitudeof the antenna current will fall below normal value as the natural period of the antenna increases. On the other hand,cif the controlling current is decreased, the inductance of the two coils will increase and the antenna potential and current will increase. Since, however, the lnductive losses are much less than when the controlling current is increaslng, the maximum amplitude of the current will becomegreater than under normal conditions. Hence, the variation 1n the antenna current which may be produced with a given variation of the controlling current, will be much greater than when the coils are connected in series with the antenna. Thus, it will be seen that by modifying the connection of the inductive device or by varying the adjustment thereof to work on either side of the tuning curve, it will be possible to produce various relations between the value of the controlling current and the antenna current. In any case, however, the antenna current will vary as a function of the variations in the controlling current.

The controlling current for the coils 7 and 8 may be supplied by any convenient source of direct current which can be varied so as to vary the antenna current in a desired manner. In the drawing I have indicated a means for securing the controlling current which is especially adapted for use in cases .where an ordinary source of the required voltage and output is not available. As indicated in the drawing, the circuit of the magnetizing coils 7 and 8 includes an inductance' 9 which may be loosely coupledto the tuning inductance 10 in the antenna. The current derived in this way is rectified by means of the mercury rectifier 11 and caused to flow through the transmitter 12 1 and coils 7 and 8. It will of course be understood that the transmitter 152 instead of being connected directly in the circuit may be included in aseparate circuit inductively related to the control circuit. The direct current source of energy 13 which is connected to the coils 7 and 8 through the inductance 14 produces a constant magnetization of the core 6. This battery is connected in such a way as to oppose the clectromotive force dcrived from the coil 9 and the rectifier 1]. With this arrangement, it will be seen that as the current flowing through the telephone increases, the magnetization of the core 6 will decrease, thereby decreasing the current throughthe coils 4 and 5. As a result, the antenna current will increase and there will be a corresponding increase in the rectified current which again reacts on the antenna circuit, etc. If the various elements are properly proportioned, this reinforcing action may become so great that considerable amounts of energy may be controlled by the telephone current. Since the potential aplied to the telephone varies as an inverse unction of the resistance of the telephone, a much greater current variation will be obtained than when a constant potential is applied to the telephone. In order that the impedance of that part of the antenna circuit including the coils 4: and 5 may be the minimum when the controlling current in the coils 7 and 8 is a maximum. it will be found desirable to includein the circuit an adjustable condenser 15.

WVhat I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination with an electric circuit supplied by a source of high frequency cur rent of a second circuit so related to the first as to receive energy therefrom, rectifying means in said second circuit, means for causing the rectified current in the second circuit to react upon the first circuit so-as to control the current therein, and means for varying the current in the second circuit.

2. The combination with an electric circuit supplied by a source of high frequency current of a second circuit so related to the first as to receive energy therefrom, rectifying means in said second circuit, a magnetizing winding in said second circuit, reactance included in the first circuit and inductively related to said magnetizing Winding in such a manner that the current through said reactance will vary with variations in the current flowing in said magnetizing winding, and means for varying the current in the second circuit.

3. The method of producing a pulsating current which consists in applying to avariable resistance device from a circuit external to that in which the resistance is connected an electromotive force which varies as an inverse function of the variations in said resistance.

4. The method of producing telephone currents which consists in applying to a telephone transmitter from a circuit external to that in which the transmitter is connected an electromotive force which varies as an inverse function of the variations in the resistance of the transmitter.

5. The combination with a resistance clevice, of means for varying the resistance of said device, and means for supplying to said resistance device from a circuit external to that in which it is connected an electromotive force which varies as an inverse function of the variations in said resistance.

6. The combination with a telephone transmitter, of means for supplying to the terminals of said transmitter from a circuit external to that in which it is connected an electromotive force which varies as an inverse function of the variations in the resistance of said transmitterj In witness whereof, I have hereunto set my hand this 23rd day of May, 1924;.

ERNST F. WV. ALEXANDERSON. 

